Nanostructured transition metal dichalcogenide electrocatalysts for CO2 reduction in ionic liquid

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Science  29 Jul 2016:
Vol. 353, Issue 6298, pp. 467-470
DOI: 10.1126/science.aaf4767
  1. Fig. 1 CO2 reduction performance of the TMDC catalysts, Ag NPs, and bulk Ag in the EMIM-BF4 solution.

    (A) Cyclic voltammetry (CV) curves for WSe2 NFs, bulk MoS2, Ag nanoparticles (Ag NPs), and bulk Ag in CO2 environment. Inset shows the current densities in low overpotentials. (B) CO and H2 overall faradaic efficiency (FE) at different applied potentials for WSe2 NFs. The error bars represent SD of four measurements. (C) CO formation TOF of WSe2 NFs, bulk MoS2, and Ag NPs in IL electrolyte at overpotentials of 54 to 650 mV. At 54 mV overpotential, Ag NPs’ result is zero. (D) Overview of different catalysts’ performance at different overpotentials (η). All TMDC and Ag NP data were obtained from chronoamperometry experiments under identical conditions. Data for other catalysts are from (12).

  2. Fig. 2 Artificial leaf.

    (A) Schematic of the cell design. (B) Rate of product formation (mol/s) with respect to different Sun illuminations. (C) Calculated solar-to-fuel efficiency (SFE) of photochemical process using the WSe2/IL cocatalyst system. Our calculation indicates ~4.6% SFE, which is limited by the maximum efficiency of PV-a-si-3jn (~6.0%). Error bars indicate uncertainty in the calculated SFE (table S5) (13).

  3. Fig. 3 Electrochemical impedance spectroscopy of CO2 reduction using WSe2 NFs, bulk MoS2, and Ag NPs at 150 mV overpotential.
  4. Fig. 4 Density functional theory analysis.

    (A) Calculated free energy diagrams for CO2 electroreduction to CO on Ag(111), Ag55 NPs, MoS2, WS2, MoSe2, and WSe2 NFs at 0 V RHE. (B) Calculated partial density of states of the d band (spin-up) of the surface Ag atom of Ag55. (C) Calculated partial density of states of the surface bare metal edge atom (W) of the WSe2 NFs. The calculations of the Ag systems are at CO coverage of 1/16 ML; those of the TMDC systems are at CO coverage of 1 ML. See (13) for details of the coverage effects in the TMDC systems.

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